The invention relates to the field of the manufacture of objects provided with profiled elements made of plastic, such as windows provided with ornamental or sealing strips. It relates more particularly to a process for fashioning a portion of a profiled bead extruded onto an object, and to articles resulting therefrom, as well as to a device especially designed to implement this process.
It is generally known to deposit profiled beads of polymer, for example along the edge of a pane, by continuous extrusion, and to use them directly as a sealing strip, especially for windows fitted into a frame by bonding. Suitable sections of strips help, on the one hand, to centre the window when fitting it into a frame or chassis, for example into a body opening, and guarantee, on the other hand, the position of the window while the adhesive usually employed is curing. Compared with the injection moulding of such strips, which is also known, extrusion has the advantage of greater flexibility since it is not necessary to keep a specific mould for each shape of pane, but all that is required is to guide an extrusion die of calibrated cross section along the edge of the pane, the extrusion die being controlled by a programmable robot, with a defined, generally continuous, flow of material.
Sometimes it is also required to cover corner parts in the window opening with the bead of the sealing strip. Compared with the main cross section of the profiled bead, which is fixedly predetermined by the calibrated shape of the extrusion die, more material is needed in such corner regions. According to Patent DE-C-196 04 397, there exists an extrusion die whose cross section can automatically increase in the corner regions of a pane. Furthermore, the die comprises two channels for supplying the polymer, in each of which the volume flow rate may be controlled independently of one another by valves. Overall, the additional material needed compared with the bead of normal profile is extruded in a continuous path with the desired cross section. However, such a die is very expensive to manufacture.
It is also known to subsequently touch up the extruded strip in such regions where modification of the profile is required, or in xe2x80x9ccriticalxe2x80x9d regions such as the join region between the start and end of the extrusion.
Certain existing solutions thus modify the cross section of the bead by cutting off a defined portion of the bead in a corner region or join region and by filling the gaps thus created by injecting an additional material which joins up with the profiled bead (EP-B 0,524,060), or add additional material for filling the corners by injection onto the continuous profiled bead of uniform cross section in a work phase after the extrusion (cf. DE-C-195 37 693).
In practice, the windows have hitherto been removed from the extrusion station before the profiled bead is touched up and are repositioned in a separate touch-up station. The extrusion station therefore has the best possible occupancy since, before injection of additional material or partial cutting and filling of the gap created, it is necessary to wait for a hold time until the extruded material has stabilized sufficiently.
It is also already known, from Patent DE 4,445,258 C2, to touch up the join region between the start and end of a profiled bead made of extruded polymer surrounding the edge of a pane by means of a multipart compression mould which executes a closure movement going from the centre of the pane towards the external edge so that the excess material in the join region is expelled to the outside and is detached therefrom by a cutting edge carried by the compression tool. However, the particular direction of operation of that known device leads to a bulky system for which there is not enough space in the immediate vicinity of an extrusion station. Thus, all the windows in that device must also be refitted and repositioned separately.
Another known postforming tool (DE-U-90 11 573) for profiled beads of extruded polyurethane is also designed in such a way that the panes must be positioned with respect to the device and cannot therefore be touched up directly in the extrusion station.
Touch-up processes with transfer of the window furthermore have the drawback that the solutions proposed do not always give exactly the expected result with, in particular, visible transition marks on the postformed region which are due to the addition of fresh material alongside the earlier extruded material which has already at least partially cured.
It is therefore desired to find improved processes, with a more reliable appearance result, preferably by reducing the cost compared with that currently borne, in the techniques using postforming or filling especially by injection moulding, by the succession of steps of transferring each window provided with the moulded profiled bead out of the extrusion station, of fitting and positioning the following touch-up station and finally of fashioning the critical portion.
Thus, the object of the invention is to present a process which markedly improves the touching-up, in particular by decreasing the hold time for the postforming of critical regions of a profiled bead, especially corner regions and/or join regions. A corresponding device, which is also advantageously as compact as possible, especially suitable for implementing this process, may also be proposed.
The subject of the invention is thus a process for the fashioning of a portion of a profiled bead extruded onto an object, in particular a pane, in which process an initially shapeless mass of material is produced in the portion in question and is given the desired final shape by contact with a shaped surface of a moving tool, any excess material being automatically expelled from the tool in order to be removed, characterized in that the mass of material is produced by the superposition of two segments of the extruded strip, with the following steps:
the extrusion die is guided along a first segment of the intended path of the profiled bead, including the portion to be fashioned;
the die is taken away from the object and is moved, relative to the object, to an adjacent position of the portion to be fashioned;
the die is guided again, along a second segment of the path of the profiled bead, also including the portion to be fashioned.
The process according to the invention is characterized by the fact that material needed for the final fashioning is supplied directly at the time of extrusion, so that after the die has left the region in question, the touch-up operation can be started at the same time as the extrusion stops.
The saving in production time represents a certain economical advantage.
Furthermore, since the touch-up operation is started immediately, any difference in appearance between the region which is extruded ir the usual manner and the region which has undergone the additional treatment is lessened, since the material of the extruded part has not yet been cured and/or crosslinked significantly by the time the fashioning of the adjacent part is started.
This process is particularly useful for the local production of particular shapes in limited regions of the strip, in particular for corner regions which are more difficult to produce the more acute-angled the corner.
According to one particular embodiment for fashioning a corner, especially an acute-angled corner, the die is moved relative to the object by changing the relative orientation of the die with respect to the object, especially by rotation through the desired angle, and the die is guided, in the new direction thus obtained, along the following side of the object.
In one particular case, the first and/or second segment extend/extends beyond the perimeter of the object so that the fashioned portion projects beyond the end face of the object.
In general, it is not necessary to interrupt the flow of material during intermediate movement of the die.
According to an advantageous variant, the accumulation of material is formed by moving the die, after the first segment has been extruded, by passing it over that region of the first segment which includes the portion to be fashioned. In the region in question, the material thus forms a kind of ribbon folded back on itself, in which the superposed layers (or folds) adhere perfectly to each other.
In this regard, the subject of the invention is also novel products, especially:
an article, especially a window, comprising an object provided with a profiled bead extruded onto the object and having a fashioned portion, characterized in that the fashioned portion consists of a continuous folded ribbon of extruded material, in which ribbon the opposed surfaces of the fold or folds adhere to each other along a possibly pellicular interface, which ribbon is fashioned by contact with a shaped surface;
an article, especially a window, comprising an object, especially a pane, provided with a profiled bead extruded onto the object and having at least one corner portion, characterized in that at least one corner portion consists of the superposition of at least two partial beads which adhere to each other along a possibly pellicular interface, which superposed bead portion is fashioned by contact with a shaped surface.
In fact, depending especially on the plastic used, on the extrusion rate, on the ambient temperature or the ambient moisture content, the material deposited on the first partial bead may be partially modified before the material of the second partial bead has been superposed on it. Thus, the plastic in the fashioned region is in general relatively heterogeneous, although giving the bead sufficient cohesion by the respective layers adhering to each other.
In extreme cases, there may even form on the surface of the first partial bead a kind of skin or film which is completely compatible with the material deposited on top of it just afterwards, but which may be visible if a longitudinal section of the product is examined.
The extruded material is advantageously of the thermoplastic type, for example a thermoplastic elastomer (TPE) or a thermoplastic olefin (TPO). Materials not having an excessive tack are preferred so as to facilitate the fashioning operations, especially the removal of the shaped surface.
With thermoplastics, it may be advantageous to heat the bead portion or portions to be fashioned before and/or during the fashioning.
The object of the invention is also a device for the fashioning of a portion of a profiled bead extruded onto an objectxe2x80x94in particular onto a panexe2x80x94fastened in a treatment station, in particular for implementing the process according to the invention, in which device a moving calibrated tool may be brought into contact with the said strip portion, comprising in initially shapeless accumulation of material, and applies against the latter a shaped surface corresponding to the uniform profile of the profiled bead, and in which device means are provided for cutting and removing the excess material, being characterized by the fact that the tool is connected in a locally adjustable manner to the treatment station provided for laying down the profiled bead and can be moved between a rest position and a working position in contact with the object fastened in the treatment station, by means of an actuating device, and in that means are provided for the correct and automatic adjustment of the relative position between the tool and the object.
According to a preferred embodiment of the invention, the postforming device will be automatically positioned directly after the extrusion of an accumulation of material at the respective critical point along the profiled bead, after the extrusion die has continued its travel without the window to be treated having been transferred and also before the extruded material has been cured, in order to give the desired dimensions to that region of the profiled bead in question, so that it matches, without any transition, the dimensions of the adjacent portion of profiled bead being formed, while any excess material will be expelled and automatically removed.
Thus, for the same occupancy of the extrusion station, a substantial time saving will be obtained in the subsequent treatment of the critical regions of the profiled bead as they can now be formed in line during the continuation of the extrusion process, and therefore without additional handling of the window which is positioned only once in the extrusion station.
Further advantages of the process are a substantial reduction in the risk of damage when handling the windows and a reduction in or even elimination of the costs of touching up for removing the excess material from the bead. Finally, the need for space for the additional touch-up station in the manufacturing plant also disappears.
In the case of filling corner regions, according to a development of the process, the necessary accumulation of material will be produced by taking the extrusion die away from the edge of the window, rotating it and applying it again at the point of separation by superposing two profile portions. Because of the plasticity of the material, the accumulation is initially shapeless. However, just after the extrusion die has continued its travel, it will be adjusted to the cross section of the profiled bead by means of the automatically positionable tool.
Further features and advantages of the subject of the invention will emerge from the following detailed description and the illustration of an example of the implementation of a process and of an embodiment of a device according to the invention.
In the example of the postforming of a corner of a profiled bead made of thermoplastic elastomer (TPE) which is deposited on a window: